1. Field of the Invention
The present invention relates to a locking device for use with an automotive seat, and in particular to a longitudinal locking device for locking and unlocking a movable part of the seat.
2. Description of Prior Art
An automotive seat is provided with a locking device for locking and unlocking the movable and adjustable parts or devices associated with the seat, such as a reclining device for adjusting an inclination angle of seat back of the seat, or a device for fine adjustment of inclination of an armrest provided in the seat.
Various locking devices of this kind are made available for a particular purpose in the seat. One of them is a well-known gear locking type comprising a plural number of gears, wherein some of them are combined together to form a locking gear, while another of them form in combination an unlocking gear. But, this conventional device is obviously a very complicated structure requiring a high precision in plural associated parts thereof. Further, when an incomplete or half locking occurs therein, the gears are wobbled and contacted with one another to generate an unpleasant or noisy sound.
Recently, instead of such intricate gear structure, there is made available a spring locking device which is simple in using one coil spring and a spindle or tubular body to form a locking and unlocking element, as disclosed from the Japanese Laid-Open Pub. 50-95710 for example. According to this prior art, the coil spring is wound around the spindle, such that the spring itself can be twisted into a frictional contact about the spindle for a locking action. However, this will not give a smooth and sufficient locking effect in practical operation, and will generate a keen objectionable noise therefrom.